Java中的线程同步，IllegalMonitorStateException [英] Threads synchronizing in Java, IllegalMonitorStateException

问题描述

我正在尝试同步两个线程-主"线程和一个可运行线程.我得到了IllegalMonitorStateException，但是我不完全理解您没有对象的锁"的含义.

I am trying to synchronize two threads - the "Main" thread, and a runnable. I get the IllegalMonitorStateException, but I do not completelty understand what "you do not have the lock of the object" means.

这是我的代码:

public class ThreadsTest {
    private static ThreadsTest instance;
    public volatile boolean flag = false;

    public void doStuff() {
        System.out.println("first");

        this.flag = true;

    }

    public Runnable mDrawer = new Runnable() {

        public void run() {
            synchronized (ThreadsTest.getInstance()) {
                while (flag == false)
                    try {
                        wait();
                    } catch (InterruptedException ie) {
                        System.out.println("second");
                    }
            }



        }
    };

    public static ThreadsTest getInstance() {
        if (ThreadsTest.instance == null) {
            ThreadsTest.instance = new ThreadsTest();
        }
        return ThreadsTest.instance;
    }

    private ThreadsTest() {
    }

    public static void main(String[] args) {
        ThreadsTest t = ThreadsTest.getInstance();
        t.mDrawer.run();
        t.doStuff();

    }
}

推荐答案

您只能在同步对象上调用wait()方法.
因此，由于您具有synchronized (ThreadsTest.getInstance())，因此必须编写ThreadsTest.getInstance().wait().

You may call wait() method only on objects you synchronizing on.
So, since you have synchronized (ThreadsTest.getInstance()), you must write ThreadsTest.getInstance().wait().

不确定您要在此处进行的测试是什么，如果只是基本的线程同步示例，则应将代码更改为

Not sure what you trying to test here exactly, if it's just basic thread sync sample, then you should change your code to

public class ThreadsTest {
    private static ThreadsTest instance;
    public volatile boolean flag = false;

    public void doStuff() {
        System.out.println("first");
        this.flag = true;
        synchronized (getInstance()) {
            getInstance().notifyAll();
        }
    }

    public Runnable mDrawer = new Runnable() {

        public void run() {
            synchronized (ThreadsTest.getInstance()) {
                while (flag == false)
                    try {
                        ThreadsTest.getInstance().wait();
                    } catch (InterruptedException ie) {
                        System.out.println("second");
                    }
            }



        }
    };

    public static ThreadsTest getInstance() {
        if (ThreadsTest.instance == null) {
            ThreadsTest.instance = new ThreadsTest();
        }
        return ThreadsTest.instance;
    }

    private ThreadsTest() {
    }

    public static void main(String[] args) throws InterruptedException {
        ThreadsTest t = ThreadsTest.getInstance();
        new Thread(t.mDrawer).start();
        Thread.sleep(1000L); // let other thread start, so it won't skip our notify()
        t.doStuff();
    }
}

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